1. Field
The present invention relates to a method of driving a multi-level variable resistive memory device and a multi-level variable resistive memory device.
2. Description of the Related Art
Memory devices using resistance materials to store data in a non-volatile manner include; phase change random access memory (PRAM), resistive RAM (RRAM), and ferroelectric RAM (FRAM). In contrast, dynamic RAM (DRAM) and contemporary flash memory store data using electrical charge to store data, although DRAM is not nonvolatile in its operating nature. Instead of variations in electrical charge non-volatile memory devices using resistance materials store data in relation to change of a phase state change for a material like a chalcogenide alloy (PRAM), change in resistance of variable resistance materials (RRAM), and change in a polarization phenomenon of ferroelectric materials (FRAM).
Contemporary memory devices regardless of data storage mechanism, are characterized by continuing attempts to shrink memory cell size, increase integration density, and/or increase data storage density per unit area occupied by the memory device. Among other techniques used to increase data storage density, memory cells capable of storing multiple data bits are increasingly common.